The Contractor shall perform a population-based case-control study on the risk of rheumatoid arthritis in oral contraceptive users. The aims of the project are to determine whether exposure to specific contraceptive steroids, currently or in the past, reduce the current or lifetime risk of developing rheumatoid arthritis. Sub-analyses will be undertaken to clarify the nature of the association according to characteristics of hormone exposure, such as duration of steroid use or cumulative dose of estrogen or specific progestins. Where possible, special sub-groups of women at particularly high risk will be identified.